Question

I’ve seen code like the following in some JS libraries:

var i;
for (i = 20; i >= 0; i -= 1) 
{
}

I wonder why they would choose to decrement i in this fashion. Is there something problematic about using ++ and -- in javascript?

Answer 1

Douglas Crockford, aka the godfather of JavaScript, discourages the ++.

Confusing Pluses and Minuses

Be careful to not follow a + with + or ++. This pattern can be
confusing. Insert parens between them to make your intention clear.

total = subtotal + +myInput.value;

is better written as

total = subtotal + (+myInput.value);

so that the + + is not misread as ++.

Personally, the — or ++ is completely okay in a for loop as its meaning is very clear. I tend to follow most of Crockford’s guidelines though because its generally the basis of JS conventions.

See more here.